1. Field of the Invention
This invention relates to a composition of dielectric for a plasma display panel.
2. Description of the Related Art
Nowadays, there have been actively developed flat display devices such as a liquid crystal display (LCD), a field emission display(FED), a plasma display panel (PDP) and so on. In the flat display devices, the PDP has advantages in that it permits an easier manufacturing according to its simple structure, and a higher efficiency in the brightness and emission in comparison to other flat display devices. Further, the PDP has advantages in that it has not only a memory function, a light view angle more than 160.degree., but also it permits an implementation of a large-scale screen more than 40 inches.
Referring to FIG. 1, there is shown a conventional PDP that includes a lower glass substrate 14 mounted with an address electrode 2, a lower dielectric layer 18 applied on the lower glass substrate 14 in a predetermined thickness to form a wall charge, barrier ribs 8 defined on the lower dielectric layer 18 to divide each discharging cell, a fluorescent layer 6 excited and radiated by a light generated during the plasma discharge, a transparent electrode 4 defined on the upper glass substrate 16, an upper dielectric layer 12 applied on the upper glass substrate 16 and the transparent electrode 4 in a predetermined thickness to form a wall charge, and a protective layer 10 applied on the upper dielectric layer 12 to protect the upper dielectric layer 12 from any sputtering due to the discharge. If a predetermined voltage(e.g., 200 V) is applied to the address electrode 2 and the transparent electrode 4, then a plasma discharge is generated in the inner side of the discharging cell by means of electrons emitted from the address electrode 2. More specifically, electrons emitted from the electrode 2 collides with atoms in a mixed gas of He gas and Xe gas or a mixed gas of Ne gas and Xe gas sealed in the discharging cell and ionizes the atoms in the mixed gas, thereby causing an emission of secondary electrons. The secondary electrons repeat a collision with the atoms in the mixed gas to thereby ionize the mixed gas atoms sequentially. In other words, they enter an avalanche process having electrons and ions increased into twice. A light generated in the avalanche process radiates the fluorescent layer of red(R), green(G), and blue(B) colors. The R, G and B lights emitted at the fluorescent layer progress, via the protective layer 10, the upper dielectric layer 12 and the transparent electrode 4, into the upper glass substrate 16 so as to display an image. It is necessary for the upper dielectric layer 12 and the lower dielectric layer 18 to have a characteristic different from each other. For example, the upper dielectric layer 12 requires to have a high transmission coefficient because it must transmit a light radiated from the fluorescent layer 6; whereas the lower dielectric layer 18 not only requires to have a high density structure and a high reflection coefficient because it must perform functions of improving a radiation efficiency as well as preventing a diffusion by reflecting the light radiated from the fluorescent layer 6 toward the upper glass substrate 16, but also it requires to have characteristics of a low thermal expansion coefficient, a thermal stability and a low dielectric constant and so on so as to prevent a crack.
A dielectric layer and a method thereof for meeting the requirements as mentioned above were disclosed in the Japanese patent publication No. 8-119665. The dielectric layer in the above Japanese patent publication No. 8-119665 has a composition as shown in Table 1. The composition ratio in Table 1 was given assuming a weight of dielectric layer to be 100 weight percent.
TABLE 1 Composition of dielectric layer COMPONENT PbO SiO.sub.2 B.sub.2 O.sub.3 ZnO Al.sub.2 O.sub.3 WEIGHT % 60-70 12-17 8-15 5-12 0.1-5
An alternative method of manufacturing the dielectric layer is disclosed in the Japanese Patent Publication No. 8-119665. In the method, first, a compound glass including PbO of 60 to 70 weight % or a glass-ceramics material mixing an oxide filler with the compound glass is prepared into a powder below 10 .mu.m. Subsequently, the powder is pasted into a state mixed with an organic vehicle and then the pasted powder is screen printed on the glass substrate into a thickness of 20 to 30 .mu.m. Finally, the paste screen-printed on the glass substrate is dried for 20 to 30 minutes at a temperature of 100.degree. C. and thereafter is sintered at a temperature range of 500 to 550.degree. C., thereby making a dielectric layer.
The dielectric layer manufactured in a manner as described above has problems in that it causes a delay phenomenon in an addressing time because its dielectric constant has a relatively high value of 12 to 15 and that it causes an increase in a weight of devices and the entire weight because the gravity of Pb is heavy. Another problem is glass that the glass containing PbO causes pollution.